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	$212.84	6.244%	$226.1297	$226.13	$226.15	$226.10
Purchase #2	$135.61	10.350%	$149.6456	$149.65	$149.65	$149.60
Purchase #3	$51.85	4.712%	$54.2932	$54.29	$54.30	$54.30
Purchase #4	$118.56	10.144%	$130.5867	$130.59	$130.60	$130.60
Purchase #5	$184.36	6.734%	$196.7748	$196.77	$196.75	$196.80
Purchase #6	$70.29	3.258%	$72.58	$72.58	$72.60	$72.60
Purchase #7	$163.77	6.271%	$174.04	$174.04	$174.05	$174.00
7 purchase totals =	$937.28		$1,004.0500	$1,004.05	$1,004.10	$1,004.00