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	$152.95	9.250%	$167.0979	$167.10	$167.10	$167.10
Purchase #2	$174.88	12.192%	$196.2014	$196.20	$196.20	$196.20
Purchase #3	$196.86	7.710%	$212.0379	$212.04	$212.05	$212.00
Purchase #4	$53.51	10.260%	$59.0001	$59.00	$59.00	$59.00
Purchase #5	$195.49	12.162%	$219.2655	$219.27	$219.25	$219.30
Purchase #6	$39.28	6.855%	$41.9726	$41.97	$41.95	$42.00
Purchase #7	$113.83	12.719%	$128.308	$128.31	$128.30	$128.30
7 purchase totals =	$926.80		$1,023.8834	$1,023.89	$1,023.85	$1,023.90