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	$127.46	3.112%	$131.4266	$131.43	$131.45	$131.40
Purchase #2	$205.26	8.583%	$222.8775	$222.88	$222.90	$222.90
Purchase #3	$136.77	11.727%	$152.809	$152.81	$152.80	$152.80
Purchase #4	$166.76	4.391%	$174.0824	$174.08	$174.10	$174.10
Purchase #5	$156.79	10.160%	$172.7199	$172.72	$172.70	$172.70
Purchase #6	$92.75	3.516%	$96.0111	$96.01	$96.00	$96.00
Purchase #7	$130.26	9.596%	$142.7597	$142.76	$142.75	$142.80
7 purchase totals =	$1,016.05		$1,092.6862	$1,092.69	$1,092.70	$1,092.70