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	$161.73	3.117%	$166.7711	$166.77	$166.75	$166.80
Purchase #2	$154.25	7.689%	$166.1103	$166.11	$166.10	$166.10
Purchase #3	$188.33	4.187%	$196.2154	$196.22	$196.20	$196.20
Purchase #4	$184.72	3.619%	$191.405	$191.41	$191.40	$191.40
Purchase #5	$215.27	8.781%	$234.1729	$234.17	$234.15	$234.20
Purchase #6	$170.75	6.213%	$181.3587	$181.36	$181.35	$181.40
Purchase #7	$79.58	3.540%	$82.3971	$82.40	$82.40	$82.40
7 purchase totals =	$1,154.63		$1,218.4305	$1,218.44	$1,218.35	$1,218.50