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	$116.90	8.678%	$127.0446	$127.04	$127.05	$127.00
Purchase #2	$73.72	12.645%	$83.0419	$83.04	$83.05	$83.00
Purchase #3	$53.98	7.148%	$57.8385	$57.84	$57.85	$57.80
Purchase #4	$63.44	6.114%	$67.3187	$67.32	$67.30	$67.30
Purchase #5	$6.76	7.462%	$7.2644	$7.26	$7.25	$7.30
Purchase #6	$197.96	7.813%	$213.4266	$213.43	$213.45	$213.40
Purchase #7	$175.73	11.223%	$195.4522	$195.45	$195.45	$195.50
7 purchase totals =	$688.49		$751.3869	$751.38	$751.40	$751.30