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	$235.47	3.738%	$244.2719	$244.27	$244.25	$244.30
Purchase #2	$209.77	10.372%	$231.5273	$231.53	$231.55	$231.50
Purchase #3	$97.71	5.758%	$103.3361	$103.34	$103.35	$103.30
Purchase #4	$72.69	6.383%	$77.3298	$77.33	$77.35	$77.30
Purchase #5	$222.64	6.465%	$237.0337	$237.03	$237.05	$237.00
Purchase #6	$134.28	7.446%	$144.2785	$144.28	$144.30	$144.30
Purchase #7	$107.73	4.370%	$112.4378	$112.44	$112.45	$112.40
7 purchase totals =	$1,080.29		$1,150.2151	$1,150.22	$1,150.30	$1,150.10