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	$235.88	3.429%	$243.9683	$243.97	$243.95	$244.00
Purchase #2	$228.89	9.419%	$250.4491	$250.45	$250.45	$250.40
Purchase #3	$177.75	10.429%	$196.2875	$196.29	$196.30	$196.30
Purchase #4	$157.27	3.142%	$162.2114	$162.21	$162.20	$162.20
Purchase #5	$105.63	5.618%	$111.5643	$111.56	$111.55	$111.60
Purchase #6	$171.49	9.201%	$187.2688	$187.27	$187.25	$187.30
Purchase #7	$32.58	6.368%	$34.6547	$34.65	$34.65	$34.70
7 purchase totals =	$1,109.49		$1,186.4041	$1,186.40	$1,186.35	$1,186.50