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	$244.87	5.413%	$258.1248	$258.12	$258.10	$258.10
Purchase #2	$96.49	9.406%	$105.5658	$105.57	$105.55	$105.60
Purchase #3	$28.38	12.163%	$31.8319	$31.83	$31.85	$31.80
Purchase #4	$123.82	5.445%	$130.562	$130.56	$130.55	$130.60
Purchase #5	$71.48	9.566%	$78.3178	$78.32	$78.30	$78.30
Purchase #6	$66.46	3.656%	$68.8898	$68.89	$68.90	$68.90
Purchase #7	$235.91	6.326%	$250.8337	$250.83	$250.85	$250.80
7 purchase totals =	$867.41		$924.1258	$924.12	$924.10	$924.10