Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$174.33	6.281%	$185.2797	$185.28	$185.30	$185.30
Purchase #2	$233.92	11.773%	$261.4594	$261.46	$261.45	$261.50
Purchase #3	$185.93	3.261%	$191.9932	$191.99	$192.00	$192.00
Purchase #4	$162.26	12.308%	$182.231	$182.23	$182.25	$182.20
Purchase #5	$140.51	8.804%	$152.8805	$152.88	$152.90	$152.90
Purchase #6	$194.98	8.755%	$212.0505	$212.05	$212.05	$212.10
Purchase #7	$142.54	3.661%	$147.7584	$147.76	$147.75	$147.80
7 purchase totals =	$1,234.47		$1,333.6527	$1,333.65	$1,333.70	$1,333.80