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	$103.86	7.325%	$111.4677	$111.47	$111.45	$111.50
Purchase #2	$157.39	3.405%	$162.7491	$162.75	$162.75	$162.70
Purchase #3	$144.89	3.280%	$149.6424	$149.64	$149.65	$149.60
Purchase #4	$90.61	9.573%	$99.2841	$99.28	$99.30	$99.30
Purchase #5	$229.92	11.156%	$255.5699	$255.57	$255.55	$255.60
Purchase #6	$152.33	12.487%	$171.3514	$171.35	$171.35	$171.40
Purchase #7	$166.71	7.663%	$179.485	$179.49	$179.50	$179.50
7 purchase totals =	$1,045.71		$1,129.5496	$1,129.55	$1,129.55	$1,129.60