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	$123.75	3.353%	$127.8993	$127.90	$127.90	$127.90
Purchase #2	$29.52	7.393%	$31.7024	$31.70	$31.70	$31.70
Purchase #3	$115.71	13.698%	$131.56	$131.56	$131.55	$131.60
Purchase #4	$151.50	9.498%	$165.8895	$165.89	$165.90	$165.90
Purchase #5	$26.68	3.819%	$27.6989	$27.70	$27.70	$27.70
Purchase #6	$240.87	11.815%	$269.3288	$269.33	$269.35	$269.30
Purchase #7	$187.69	12.783%	$211.6824	$211.68	$211.70	$211.70
7 purchase totals =	$875.72		$965.7613	$965.76	$965.80	$965.80