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	$224.87	4.718%	$235.4794	$235.48	$235.50	$235.50
Purchase #2	$101.92	7.837%	$109.9075	$109.91	$109.90	$109.90
Purchase #3	$135.25	12.592%	$152.2807	$152.28	$152.30	$152.30
Purchase #4	$26.42	10.725%	$29.2535	$29.25	$29.25	$29.30
Purchase #5	$208.72	6.478%	$222.2409	$222.24	$222.25	$222.20
Purchase #6	$163.98	4.686%	$171.6641	$171.66	$171.65	$171.70
Purchase #7	$229.81	9.178%	$250.902	$250.90	$250.90	$250.90
7 purchase totals =	$1,090.97		$1,171.7281	$1,171.72	$1,171.75	$1,171.80