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	$238.76	3.507%	$247.1333	$247.13	$247.15	$247.10
Purchase #2	$13.33	6.441%	$14.1886	$14.19	$14.20	$14.20
Purchase #3	$215.82	3.191%	$222.7068	$222.71	$222.70	$222.70
Purchase #4	$94.98	10.185%	$104.6537	$104.65	$104.65	$104.70
Purchase #5	$122.74	13.301%	$139.0656	$139.07	$139.05	$139.10
Purchase #6	$184.91	4.614%	$193.4417	$193.44	$193.45	$193.40
Purchase #7	$90.46	8.649%	$98.2839	$98.28	$98.30	$98.30
7 purchase totals =	$961.00		$1,019.4736	$1,019.47	$1,019.50	$1,019.50