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	$196.89	7.707%	$212.0643	$212.06	$212.05	$212.10
Purchase #2	$129.34	3.854%	$134.3248	$134.32	$134.30	$134.30
Purchase #3	$94.82	10.360%	$104.6434	$104.64	$104.65	$104.60
Purchase #4	$96.81	13.427%	$109.8087	$109.81	$109.80	$109.80
Purchase #5	$134.79	3.428%	$139.4106	$139.41	$139.40	$139.40
Purchase #6	$64.96	3.308%	$67.1089	$67.11	$67.10	$67.10
Purchase #7	$161.98	5.511%	$170.9067	$170.91	$170.90	$170.90
7 purchase totals =	$879.59		$938.2674	$938.26	$938.20	$938.20