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	$88.68	13.861%	$100.9719	$100.97	$100.95	$101.00
Purchase #2	$103.51	11.483%	$115.3961	$115.40	$115.40	$115.40
Purchase #3	$69.52	7.766%	$74.9189	$74.92	$74.90	$74.90
Purchase #4	$76.39	12.728%	$86.1129	$86.11	$86.10	$86.10
Purchase #5	$78.56	13.450%	$89.1263	$89.13	$89.15	$89.10
Purchase #6	$193.54	11.658%	$216.1029	$216.10	$216.10	$216.10
Purchase #7	$209.85	4.751%	$219.82	$219.82	$219.80	$219.80
7 purchase totals =	$820.05		$902.4490	$902.45	$902.40	$902.40