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	$201.32	13.404%	$228.3049	$228.30	$228.30	$228.30
Purchase #2	$79.72	13.277%	$90.3044	$90.30	$90.30	$90.30
Purchase #3	$61.78	11.311%	$68.7679	$68.77	$68.75	$68.80
Purchase #4	$67.30	6.558%	$71.7135	$71.71	$71.70	$71.70
Purchase #5	$61.90	5.435%	$65.2643	$65.26	$65.25	$65.30
Purchase #6	$187.49	6.842%	$200.3181	$200.32	$200.30	$200.30
Purchase #7	$188.82	5.856%	$199.8773	$199.88	$199.90	$199.90
7 purchase totals =	$848.33		$924.5504	$924.54	$924.50	$924.60