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	$232.62	3.501%	$240.764	$240.76	$240.75	$240.80
Purchase #2	$54.36	13.604%	$61.7551	$61.76	$61.75	$61.80
Purchase #3	$168.79	4.349%	$176.1307	$176.13	$176.15	$176.10
Purchase #4	$10.89	11.376%	$12.1288	$12.13	$12.15	$12.10
Purchase #5	$57.32	5.607%	$60.5339	$60.53	$60.55	$60.50
Purchase #6	$115.91	13.787%	$131.8905	$131.89	$131.90	$131.90
Purchase #7	$91.52	7.240%	$98.146	$98.15	$98.15	$98.10
7 purchase totals =	$731.41		$781.3490	$781.35	$781.40	$781.30