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	$40.60	3.336%	$41.9544	$41.95	$41.95	$42.00
Purchase #2	$123.80	10.294%	$136.544	$136.54	$136.55	$136.50
Purchase #3	$196.45	7.492%	$211.168	$211.17	$211.15	$211.20
Purchase #4	$61.73	3.524%	$63.9054	$63.91	$63.90	$63.90
Purchase #5	$180.29	3.445%	$186.501	$186.50	$186.50	$186.50
Purchase #6	$58.92	4.623%	$61.6439	$61.64	$61.65	$61.60
Purchase #7	$31.41	4.582%	$32.8492	$32.85	$32.85	$32.80
7 purchase totals =	$693.20		$734.5659	$734.56	$734.55	$734.50