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	$79.74	3.495%	$82.5269	$82.53	$82.55	$82.50
Purchase #2	$245.30	7.690%	$264.1636	$264.16	$264.15	$264.20
Purchase #3	$130.47	9.448%	$142.7968	$142.80	$142.80	$142.80
Purchase #4	$113.68	13.780%	$129.3451	$129.35	$129.35	$129.30
Purchase #5	$41.28	13.154%	$46.71	$46.71	$46.70	$46.70
Purchase #6	$156.51	12.806%	$176.5527	$176.55	$176.55	$176.60
Purchase #7	$89.94	11.356%	$100.1536	$100.15	$100.15	$100.20
7 purchase totals =	$856.92		$942.2487	$942.25	$942.25	$942.30