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	$124.46	5.810%	$131.6911	$131.69	$131.70	$131.70
Purchase #2	$58.29	3.720%	$60.4584	$60.46	$60.45	$60.50
Purchase #3	$50.94	4.150%	$53.054	$53.05	$53.05	$53.10
Purchase #4	$98.31	5.402%	$103.6207	$103.62	$103.60	$103.60
Purchase #5	$160.36	3.279%	$165.6182	$165.62	$165.60	$165.60
Purchase #6	$53.66	4.247%	$55.9389	$55.94	$55.95	$55.90
Purchase #7	$169.33	6.818%	$180.8749	$180.87	$180.85	$180.90
7 purchase totals =	$715.35		$751.2562	$751.25	$751.20	$751.30