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	$54.40	12.391%	$61.1407	$61.14	$61.15	$61.10
Purchase #2	$165.48	9.718%	$181.5613	$181.56	$181.55	$181.60
Purchase #3	$141.77	10.492%	$156.6445	$156.64	$156.65	$156.60
Purchase #4	$110.44	12.220%	$123.9358	$123.94	$123.95	$123.90
Purchase #5	$148.65	13.640%	$168.9259	$168.93	$168.95	$168.90
Purchase #6	$245.30	9.406%	$268.3729	$268.37	$268.35	$268.40
Purchase #7	$237.85	11.443%	$265.0672	$265.07	$265.05	$265.10
7 purchase totals =	$1,103.89		$1,225.6483	$1,225.65	$1,225.65	$1,225.60