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	$168.87	10.285%	$186.2383	$186.24	$186.25	$186.20
Purchase #2	$50.73	10.191%	$55.8999	$55.90	$55.90	$55.90
Purchase #3	$230.91	13.268%	$261.5471	$261.55	$261.55	$261.50
Purchase #4	$91.76	8.689%	$99.733	$99.73	$99.75	$99.70
Purchase #5	$35.88	10.637%	$39.6966	$39.70	$39.70	$39.70
Purchase #6	$48.65	4.538%	$50.8577	$50.86	$50.85	$50.90
Purchase #7	$222.77	4.544%	$232.8927	$232.89	$232.90	$232.90
7 purchase totals =	$849.57		$926.8653	$926.87	$926.90	$926.80