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	$91.72	6.524%	$97.7038	$97.70	$97.70	$97.70
Purchase #2	$28.56	10.539%	$31.5699	$31.57	$31.55	$31.60
Purchase #3	$89.57	10.270%	$98.7688	$98.77	$98.75	$98.80
Purchase #4	$222.71	9.718%	$244.353	$244.35	$244.35	$244.40
Purchase #5	$91.50	5.826%	$96.8308	$96.83	$96.85	$96.80
Purchase #6	$229.88	5.814%	$243.2452	$243.25	$243.25	$243.20
Purchase #7	$174.64	8.147%	$188.8679	$188.87	$188.85	$188.90
7 purchase totals =	$928.58		$1,001.3394	$1,001.34	$1,001.30	$1,001.40