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	$83.33	9.735%	$91.4422	$91.44	$91.45	$91.40
Purchase #2	$134.36	8.287%	$145.4944	$145.49	$145.50	$145.50
Purchase #3	$154.27	11.445%	$171.9262	$171.93	$171.95	$171.90
Purchase #4	$41.34	9.627%	$45.3198	$45.32	$45.30	$45.30
Purchase #5	$155.32	7.818%	$167.4629	$167.46	$167.45	$167.50
Purchase #6	$194.32	9.182%	$212.1625	$212.16	$212.15	$212.20
Purchase #7	$131.70	7.269%	$141.2733	$141.27	$141.25	$141.30
7 purchase totals =	$894.64		$975.0813	$975.07	$975.05	$975.10