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	$241.93	5.277%	$254.6966	$254.70	$254.70	$254.70
Purchase #2	$93.46	6.249%	$99.3003	$99.30	$99.30	$99.30
Purchase #3	$96.93	12.587%	$109.1306	$109.13	$109.15	$109.10
Purchase #4	$192.82	6.155%	$204.6881	$204.69	$204.70	$204.70
Purchase #5	$71.41	3.125%	$73.6416	$73.64	$73.65	$73.60
Purchase #6	$80.27	11.616%	$89.5942	$89.59	$89.60	$89.60
Purchase #7	$180.81	6.424%	$192.4252	$192.43	$192.45	$192.40
7 purchase totals =	$957.63		$1,023.4766	$1,023.48	$1,023.55	$1,023.40