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	$175.55	7.649%	$188.9778	$188.98	$189.00	$189.00
Purchase #2	$43.34	4.783%	$45.413	$45.41	$45.40	$45.40
Purchase #3	$207.89	7.658%	$223.8102	$223.81	$223.80	$223.80
Purchase #4	$135.84	12.467%	$152.7752	$152.78	$152.80	$152.80
Purchase #5	$128.56	6.665%	$137.1285	$137.13	$137.15	$137.10
Purchase #6	$196.78	3.751%	$204.1612	$204.16	$204.15	$204.20
Purchase #7	$148.49	6.583%	$158.2651	$158.27	$158.25	$158.30
7 purchase totals =	$1,036.45		$1,110.5310	$1,110.54	$1,110.55	$1,110.60