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	$70.63	4.312%	$73.6756	$73.68	$73.70	$73.70
Purchase #2	$100.83	10.647%	$111.5654	$111.57	$111.55	$111.60
Purchase #3	$58.34	6.227%	$61.9728	$61.97	$61.95	$62.00
Purchase #4	$103.38	7.623%	$111.2607	$111.26	$111.25	$111.30
Purchase #5	$70.94	11.741%	$79.2691	$79.27	$79.25	$79.30
Purchase #6	$137.84	9.225%	$150.5557	$150.56	$150.55	$150.60
Purchase #7	$249.83	6.346%	$265.6842	$265.68	$265.70	$265.70
7 purchase totals =	$791.79		$853.9835	$853.99	$853.95	$854.20