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	$206.95	13.721%	$235.3456	$235.35	$235.35	$235.30
Purchase #2	$171.82	7.742%	$185.1223	$185.12	$185.10	$185.10
Purchase #3	$79.92	8.353%	$86.5957	$86.60	$86.60	$86.60
Purchase #4	$72.92	3.753%	$75.6567	$75.66	$75.65	$75.70
Purchase #5	$88.58	11.194%	$98.4956	$98.50	$98.50	$98.50
Purchase #6	$30.39	6.381%	$32.3292	$32.33	$32.35	$32.30
Purchase #7	$240.98	9.866%	$264.7551	$264.76	$264.75	$264.80
7 purchase totals =	$891.56		$978.3002	$978.32	$978.30	$978.30