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	$191.80	10.563%	$212.0598	$212.06	$212.05	$212.10
Purchase #2	$42.94	6.846%	$45.8797	$45.88	$45.90	$45.90
Purchase #3	$224.77	12.842%	$253.635	$253.64	$253.65	$253.60
Purchase #4	$133.53	10.654%	$147.7563	$147.76	$147.75	$147.80
Purchase #5	$75.50	13.732%	$85.8677	$85.87	$85.85	$85.90
Purchase #6	$102.52	7.301%	$110.005	$110.01	$110.00	$110.00
Purchase #7	$174.77	11.524%	$194.9105	$194.91	$194.90	$194.90
7 purchase totals =	$945.83		$1,050.1140	$1,050.13	$1,050.10	$1,050.20