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	$26.92	4.277%	$28.0714	$28.07	$28.05	$28.10
Purchase #2	$37.53	4.330%	$39.155	$39.16	$39.15	$39.20
Purchase #3	$79.81	13.124%	$90.2843	$90.28	$90.30	$90.30
Purchase #4	$147.77	4.848%	$154.9339	$154.93	$154.95	$154.90
Purchase #5	$154.86	10.460%	$171.0584	$171.06	$171.05	$171.10
Purchase #6	$32.56	9.457%	$35.6392	$35.64	$35.65	$35.60
Purchase #7	$195.34	10.272%	$215.4053	$215.41	$215.40	$215.40
7 purchase totals =	$674.79		$734.5475	$734.55	$734.55	$734.60