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	$112.34	11.474%	$125.2299	$125.23	$125.25	$125.20
Purchase #2	$174.59	6.498%	$185.9349	$185.93	$185.95	$185.90
Purchase #3	$169.49	11.442%	$188.883	$188.88	$188.90	$188.90
Purchase #4	$187.54	12.145%	$210.3167	$210.32	$210.30	$210.30
Purchase #5	$98.43	7.779%	$106.0869	$106.09	$106.10	$106.10
Purchase #6	$19.29	4.615%	$20.1802	$20.18	$20.20	$20.20
Purchase #7	$184.69	8.480%	$200.3517	$200.35	$200.35	$200.40
7 purchase totals =	$946.37		$1,036.9833	$1,036.98	$1,037.05	$1,037.00