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	$53.91	10.152%	$59.3829	$59.38	$59.40	$59.40
Purchase #2	$120.66	7.801%	$130.0727	$130.07	$130.05	$130.10
Purchase #3	$150.76	3.237%	$155.6401	$155.64	$155.65	$155.60
Purchase #4	$236.96	5.512%	$250.0212	$250.02	$250.00	$250.00
Purchase #5	$221.75	9.235%	$242.2286	$242.23	$242.25	$242.20
Purchase #6	$235.74	6.253%	$250.4808	$250.48	$250.50	$250.50
Purchase #7	$77.39	3.812%	$80.3401	$80.34	$80.35	$80.30
7 purchase totals =	$1,097.17		$1,168.1664	$1,168.16	$1,168.20	$1,168.10