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	$50.96	5.440%	$53.7322	$53.73	$53.75	$53.70
Purchase #2	$169.56	7.498%	$182.2736	$182.27	$182.25	$182.30
Purchase #3	$50.39	9.497%	$55.1755	$55.18	$55.20	$55.20
Purchase #4	$238.46	11.770%	$266.5267	$266.53	$266.55	$266.50
Purchase #5	$55.45	11.619%	$61.8927	$61.89	$61.90	$61.90
Purchase #6	$58.88	7.779%	$63.4603	$63.46	$63.45	$63.50
Purchase #7	$13.72	4.118%	$14.285	$14.29	$14.30	$14.30
7 purchase totals =	$637.42		$697.3460	$697.35	$697.40	$697.40