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	$57.64	12.529%	$64.8617	$64.86	$64.85	$64.90
Purchase #2	$69.91	4.136%	$72.8015	$72.80	$72.80	$72.80
Purchase #3	$151.33	7.145%	$162.1425	$162.14	$162.15	$162.10
Purchase #4	$104.84	8.200%	$113.4369	$113.44	$113.45	$113.40
Purchase #5	$108.76	8.386%	$117.8806	$117.88	$117.90	$117.90
Purchase #6	$182.33	4.550%	$190.626	$190.63	$190.65	$190.60
Purchase #7	$97.57	7.118%	$104.515	$104.52	$104.50	$104.50
7 purchase totals =	$772.38		$826.2642	$826.27	$826.30	$826.20