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	$168.29	13.526%	$191.0529	$191.05	$191.05	$191.10
Purchase #2	$33.92	12.414%	$38.1308	$38.13	$38.15	$38.10
Purchase #3	$243.73	10.346%	$268.9463	$268.95	$268.95	$268.90
Purchase #4	$192.33	10.845%	$213.1882	$213.19	$213.20	$213.20
Purchase #5	$59.89	12.201%	$67.1972	$67.20	$67.20	$67.20
Purchase #6	$246.69	11.785%	$275.7624	$275.76	$275.75	$275.80
Purchase #7	$11.59	7.127%	$12.416	$12.42	$12.40	$12.40
7 purchase totals =	$956.44		$1,066.6938	$1,066.70	$1,066.70	$1,066.70