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	$206.32	7.451%	$221.6929	$221.69	$221.70	$221.70
Purchase #2	$152.35	6.629%	$162.4493	$162.45	$162.45	$162.40
Purchase #3	$112.36	13.287%	$127.2893	$127.29	$127.30	$127.30
Purchase #4	$146.56	7.502%	$157.5549	$157.55	$157.55	$157.60
Purchase #5	$186.34	5.578%	$196.734	$196.73	$196.75	$196.70
Purchase #6	$229.53	6.106%	$243.5451	$243.55	$243.55	$243.50
Purchase #7	$198.49	7.157%	$212.6959	$212.70	$212.70	$212.70
7 purchase totals =	$1,231.95		$1,321.9614	$1,321.96	$1,322.00	$1,321.90