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	$206.95	13.595%	$235.0849	$235.08	$235.10	$235.10
Purchase #2	$75.41	8.869%	$82.0981	$82.10	$82.10	$82.10
Purchase #3	$85.84	4.751%	$89.9183	$89.92	$89.90	$89.90
Purchase #4	$91.31	3.142%	$94.179	$94.18	$94.20	$94.20
Purchase #5	$85.77	9.161%	$93.6274	$93.63	$93.65	$93.60
Purchase #6	$86.68	3.472%	$89.6895	$89.69	$89.70	$89.70
Purchase #7	$42.54	6.470%	$45.2923	$45.29	$45.30	$45.30
7 purchase totals =	$674.50		$729.8895	$729.89	$729.95	$729.90