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	$53.88	9.764%	$59.1408	$59.14	$59.15	$59.10
Purchase #2	$118.71	12.312%	$133.3256	$133.33	$133.35	$133.30
Purchase #3	$54.40	9.812%	$59.7377	$59.74	$59.75	$59.70
Purchase #4	$176.56	13.379%	$200.182	$200.18	$200.20	$200.20
Purchase #5	$6.54	11.844%	$7.3146	$7.31	$7.30	$7.30
Purchase #6	$241.29	10.805%	$267.3614	$267.36	$267.35	$267.40
Purchase #7	$205.53	13.421%	$233.1142	$233.11	$233.10	$233.10
7 purchase totals =	$856.91		$960.1763	$960.17	$960.20	$960.10