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	$73.56	6.770%	$78.54	$78.54	$78.55	$78.50
Purchase #2	$230.31	5.591%	$243.1866	$243.19	$243.20	$243.20
Purchase #3	$44.47	13.178%	$50.3303	$50.33	$50.35	$50.30
Purchase #4	$229.70	3.646%	$238.0749	$238.07	$238.05	$238.10
Purchase #5	$147.66	3.435%	$152.7321	$152.73	$152.75	$152.70
Purchase #6	$108.72	3.361%	$112.3741	$112.37	$112.35	$112.40
Purchase #7	$163.96	6.318%	$174.319	$174.32	$174.30	$174.30
7 purchase totals =	$998.38		$1,049.5570	$1,049.55	$1,049.55	$1,049.50