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	$39.73	11.381%	$44.2517	$44.25	$44.25	$44.30
Purchase #2	$165.89	3.142%	$171.1023	$171.10	$171.10	$171.10
Purchase #3	$228.63	6.872%	$244.3415	$244.34	$244.35	$244.30
Purchase #4	$86.79	3.444%	$89.779	$89.78	$89.80	$89.80
Purchase #5	$27.82	10.773%	$30.817	$30.82	$30.80	$30.80
Purchase #6	$172.97	9.349%	$189.141	$189.14	$189.15	$189.10
Purchase #7	$222.53	9.562%	$243.8083	$243.81	$243.80	$243.80
7 purchase totals =	$944.36		$1,013.2408	$1,013.24	$1,013.25	$1,013.20