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	$117.77	5.290%	$124	$124.00	$124.00	$124.00
Purchase #2	$222.32	9.440%	$243.307	$243.31	$243.30	$243.30
Purchase #3	$59.70	7.731%	$64.3154	$64.32	$64.30	$64.30
Purchase #4	$64.71	4.460%	$67.5961	$67.60	$67.60	$67.60
Purchase #5	$146.75	4.127%	$152.8064	$152.81	$152.80	$152.80
Purchase #6	$32.69	11.144%	$36.333	$36.33	$36.35	$36.30
Purchase #7	$243.82	10.254%	$268.8213	$268.82	$268.80	$268.80
7 purchase totals =	$887.76		$957.1792	$957.19	$957.15	$957.10