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	$112.66	4.764%	$118.0271	$118.03	$118.05	$118.00
Purchase #2	$242.54	9.543%	$265.6856	$265.69	$265.70	$265.70
Purchase #3	$59.31	3.314%	$61.2755	$61.28	$61.30	$61.30
Purchase #4	$50.99	5.407%	$53.747	$53.75	$53.75	$53.70
Purchase #5	$166.76	12.520%	$187.6384	$187.64	$187.65	$187.60
Purchase #6	$98.46	5.214%	$103.5937	$103.59	$103.60	$103.60
Purchase #7	$32.75	10.729%	$36.2637	$36.26	$36.25	$36.30
7 purchase totals =	$763.47		$826.2310	$826.24	$826.30	$826.20