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	$54.63	8.242%	$59.1326	$59.13	$59.15	$59.10
Purchase #2	$185.62	4.538%	$194.0434	$194.04	$194.05	$194.00
Purchase #3	$85.49	11.317%	$95.1649	$95.16	$95.15	$95.20
Purchase #4	$240.85	6.819%	$257.2736	$257.27	$257.25	$257.30
Purchase #5	$214.55	11.825%	$239.9205	$239.92	$239.90	$239.90
Purchase #6	$84.75	6.270%	$90.0638	$90.06	$90.05	$90.10
Purchase #7	$76.81	11.355%	$85.5318	$85.53	$85.55	$85.50
7 purchase totals =	$942.70		$1,021.1306	$1,021.11	$1,021.10	$1,021.10