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	$125.67	13.593%	$142.7523	$142.75	$142.75	$142.80
Purchase #2	$123.46	3.771%	$128.1157	$128.12	$128.10	$128.10
Purchase #3	$166.80	8.619%	$181.1765	$181.18	$181.20	$181.20
Purchase #4	$73.25	12.263%	$82.2326	$82.23	$82.25	$82.20
Purchase #5	$147.25	3.805%	$152.8529	$152.85	$152.85	$152.90
Purchase #6	$145.97	13.263%	$165.33	$165.33	$165.35	$165.30
Purchase #7	$94.32	9.112%	$102.9144	$102.91	$102.90	$102.90
7 purchase totals =	$876.72		$955.3744	$955.37	$955.40	$955.40