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	$35.31	11.247%	$39.2813	$39.28	$39.30	$39.30
Purchase #2	$11.44	7.266%	$12.2712	$12.27	$12.25	$12.30
Purchase #3	$59.32	5.454%	$62.5553	$62.56	$62.55	$62.60
Purchase #4	$60.25	3.398%	$62.2973	$62.30	$62.30	$62.30
Purchase #5	$11.97	5.645%	$12.6457	$12.65	$12.65	$12.60
Purchase #6	$147.80	5.568%	$156.0295	$156.03	$156.05	$156.00
Purchase #7	$120.89	8.595%	$131.2805	$131.28	$131.30	$131.30
7 purchase totals =	$446.98		$476.3608	$476.37	$476.40	$476.40