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	$65.92	13.188%	$74.6135	$74.61	$74.60	$74.60
Purchase #2	$60.91	7.519%	$65.4898	$65.49	$65.50	$65.50
Purchase #3	$240.43	11.627%	$268.3848	$268.38	$268.40	$268.40
Purchase #4	$91.37	9.791%	$100.316	$100.32	$100.30	$100.30
Purchase #5	$234.92	8.513%	$254.9187	$254.92	$254.90	$254.90
Purchase #6	$39.59	5.786%	$41.8807	$41.88	$41.90	$41.90
Purchase #7	$116.31	6.290%	$123.6259	$123.63	$123.65	$123.60
7 purchase totals =	$849.45		$929.2294	$929.23	$929.25	$929.20