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	$175.73	8.399%	$190.4896	$190.49	$190.50	$190.50
Purchase #2	$78.78	6.305%	$83.7471	$83.75	$83.75	$83.70
Purchase #3	$49.55	9.655%	$54.3341	$54.33	$54.35	$54.30
Purchase #4	$232.96	3.502%	$241.1183	$241.12	$241.10	$241.10
Purchase #5	$168.97	6.308%	$179.6286	$179.63	$179.65	$179.60
Purchase #6	$236.27	11.515%	$263.4765	$263.48	$263.50	$263.50
Purchase #7	$49.84	7.869%	$53.7619	$53.76	$53.75	$53.80
7 purchase totals =	$992.10		$1,066.5561	$1,066.56	$1,066.60	$1,066.50