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	$176.31	7.149%	$188.9144	$188.91	$188.90	$188.90
Purchase #2	$154.41	9.164%	$168.5601	$168.56	$168.55	$168.60
Purchase #3	$153.97	5.578%	$162.5584	$162.56	$162.55	$162.60
Purchase #4	$180.48	4.850%	$189.2333	$189.23	$189.25	$189.20
Purchase #5	$50.70	9.516%	$55.5246	$55.52	$55.50	$55.50
Purchase #6	$99.93	9.864%	$109.7871	$109.79	$109.80	$109.80
Purchase #7	$248.84	7.777%	$268.1923	$268.19	$268.20	$268.20
7 purchase totals =	$1,064.64		$1,142.7702	$1,142.76	$1,142.75	$1,142.80