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	$194.98	4.691%	$204.1265	$204.13	$204.15	$204.10
Purchase #2	$64.36	11.451%	$71.7299	$71.73	$71.75	$71.70
Purchase #3	$29.25	11.316%	$32.5599	$32.56	$32.55	$32.60
Purchase #4	$128.42	5.830%	$135.9069	$135.91	$135.90	$135.90
Purchase #5	$94.62	5.354%	$99.686	$99.69	$99.70	$99.70
Purchase #6	$156.47	11.408%	$174.3201	$174.32	$174.30	$174.30
Purchase #7	$87.81	3.563%	$90.9387	$90.94	$90.95	$90.90
7 purchase totals =	$755.91		$809.2680	$809.28	$809.30	$809.20