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	$204.82	4.232%	$213.488	$213.49	$213.50	$213.50
Purchase #2	$79.95	8.122%	$86.4435	$86.44	$86.45	$86.40
Purchase #3	$149.43	10.670%	$165.3742	$165.37	$165.35	$165.40
Purchase #4	$82.61	8.425%	$89.5699	$89.57	$89.55	$89.60
Purchase #5	$184.48	10.487%	$203.8264	$203.83	$203.85	$203.80
Purchase #6	$67.70	5.368%	$71.3341	$71.33	$71.35	$71.30
Purchase #7	$52.46	8.556%	$56.9485	$56.95	$56.95	$56.90
7 purchase totals =	$821.45		$886.9846	$886.98	$887.00	$886.90