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	$106.90	5.188%	$112.446	$112.45	$112.45	$112.40
Purchase #2	$183.59	4.753%	$192.316	$192.32	$192.30	$192.30
Purchase #3	$37.88	8.685%	$41.1699	$41.17	$41.15	$41.20
Purchase #4	$135.49	5.824%	$143.3809	$143.38	$143.40	$143.40
Purchase #5	$98.56	10.736%	$109.1414	$109.14	$109.15	$109.10
Purchase #6	$134.50	10.709%	$148.9036	$148.90	$148.90	$148.90
Purchase #7	$63.62	5.458%	$67.0924	$67.09	$67.10	$67.10
7 purchase totals =	$760.54		$814.4502	$814.45	$814.45	$814.40