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	$125.26	6.437%	$133.323	$133.32	$133.30	$133.30
Purchase #2	$109.96	7.818%	$118.5567	$118.56	$118.55	$118.60
Purchase #3	$170.45	6.814%	$182.0645	$182.06	$182.05	$182.10
Purchase #4	$98.29	13.289%	$111.3518	$111.35	$111.35	$111.40
Purchase #5	$124.76	3.218%	$128.7748	$128.77	$128.75	$128.80
Purchase #6	$78.74	13.498%	$89.3683	$89.37	$89.35	$89.40
Purchase #7	$72.79	13.526%	$82.6356	$82.64	$82.65	$82.60
7 purchase totals =	$780.25		$846.0747	$846.07	$846.00	$846.20