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	$100.29	10.573%	$110.8937	$110.89	$110.90	$110.90
Purchase #2	$134.29	12.337%	$150.8574	$150.86	$150.85	$150.90
Purchase #3	$243.78	5.107%	$256.2298	$256.23	$256.25	$256.20
Purchase #4	$231.46	6.219%	$245.8545	$245.85	$245.85	$245.90
Purchase #5	$70.50	4.466%	$73.6485	$73.65	$73.65	$73.60
Purchase #6	$5.77	7.137%	$6.1818	$6.18	$6.20	$6.20
Purchase #7	$175.94	3.765%	$182.5641	$182.56	$182.55	$182.60
7 purchase totals =	$962.03		$1,026.2298	$1,026.22	$1,026.25	$1,026.30