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	$55.53	6.578%	$59.1828	$59.18	$59.20	$59.20
Purchase #2	$154.92	7.348%	$166.3035	$166.30	$166.30	$166.30
Purchase #3	$195.82	10.612%	$216.6004	$216.60	$216.60	$216.60
Purchase #4	$36.82	3.843%	$38.235	$38.24	$38.25	$38.20
Purchase #5	$242.91	13.873%	$276.6089	$276.61	$276.60	$276.60
Purchase #6	$119.40	11.486%	$133.1143	$133.11	$133.10	$133.10
Purchase #7	$147.76	7.234%	$158.449	$158.45	$158.45	$158.40
7 purchase totals =	$953.16		$1,048.4939	$1,048.49	$1,048.50	$1,048.40