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	$53.57	4.356%	$55.9035	$55.90	$55.90	$55.90
Purchase #2	$229.86	10.624%	$254.2803	$254.28	$254.30	$254.30
Purchase #3	$33.98	11.261%	$37.8065	$37.81	$37.80	$37.80
Purchase #4	$175.34	13.673%	$199.3142	$199.31	$199.30	$199.30
Purchase #5	$223.54	4.258%	$233.0583	$233.06	$233.05	$233.10
Purchase #6	$132.27	3.383%	$136.7447	$136.74	$136.75	$136.70
Purchase #7	$205.88	4.776%	$215.7128	$215.71	$215.70	$215.70
7 purchase totals =	$1,054.44		$1,132.8203	$1,132.81	$1,132.80	$1,132.80