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	$142.53	3.209%	$147.1038	$147.10	$147.10	$147.10
Purchase #2	$189.40	10.458%	$209.2075	$209.21	$209.20	$209.20
Purchase #3	$162.82	13.539%	$184.8642	$184.86	$184.85	$184.90
Purchase #4	$17.61	11.444%	$19.6253	$19.63	$19.65	$19.60
Purchase #5	$49.58	11.860%	$55.4602	$55.46	$55.45	$55.50
Purchase #6	$47.25	13.433%	$53.5971	$53.60	$53.60	$53.60
Purchase #7	$68.60	3.744%	$71.1684	$71.17	$71.15	$71.20
7 purchase totals =	$677.79		$741.0265	$741.03	$741.00	$741.10