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	$138.61	12.720%	$156.2412	$156.24	$156.25	$156.20
Purchase #2	$241.56	3.603%	$250.2634	$250.26	$250.25	$250.30
Purchase #3	$175.65	7.465%	$188.7623	$188.76	$188.75	$188.80
Purchase #4	$124.75	5.376%	$131.4566	$131.46	$131.45	$131.50
Purchase #5	$62.27	3.336%	$64.3473	$64.35	$64.35	$64.30
Purchase #6	$17.70	3.275%	$18.2797	$18.28	$18.30	$18.30
Purchase #7	$187.93	4.312%	$196.0335	$196.03	$196.05	$196.00
7 purchase totals =	$948.47		$1,005.3840	$1,005.38	$1,005.40	$1,005.40