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	$137.39	7.364%	$147.5074	$147.51	$147.50	$147.50
Purchase #2	$90.98	3.338%	$94.0169	$94.02	$94.00	$94.00
Purchase #3	$79.35	4.747%	$83.1167	$83.12	$83.10	$83.10
Purchase #4	$102.26	13.297%	$115.8575	$115.86	$115.85	$115.90
Purchase #5	$245.64	4.814%	$257.4651	$257.47	$257.45	$257.50
Purchase #6	$180.37	4.371%	$188.254	$188.25	$188.25	$188.30
Purchase #7	$189.39	4.721%	$198.3311	$198.33	$198.35	$198.30
7 purchase totals =	$1,025.38		$1,084.5487	$1,084.56	$1,084.50	$1,084.60