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	$178.44	10.296%	$196.8122	$196.81	$196.80	$196.80
Purchase #2	$97.32	13.399%	$110.3599	$110.36	$110.35	$110.40
Purchase #3	$140.88	13.496%	$159.8932	$159.89	$159.90	$159.90
Purchase #4	$124.92	6.395%	$132.9086	$132.91	$132.90	$132.90
Purchase #5	$36.56	13.276%	$41.4137	$41.41	$41.40	$41.40
Purchase #6	$223.62	11.126%	$248.5	$248.50	$248.50	$248.50
Purchase #7	$19.71	3.376%	$20.3754	$20.38	$20.40	$20.40
7 purchase totals =	$821.45		$910.2630	$910.26	$910.25	$910.30