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	$179.85	4.450%	$187.8533	$187.85	$187.85	$187.90
Purchase #2	$168.72	7.724%	$181.7519	$181.75	$181.75	$181.80
Purchase #3	$210.36	13.372%	$238.4893	$238.49	$238.50	$238.50
Purchase #4	$223.57	8.574%	$242.7389	$242.74	$242.75	$242.70
Purchase #5	$96.56	7.804%	$104.0955	$104.10	$104.10	$104.10
Purchase #6	$76.30	9.199%	$83.3188	$83.32	$83.30	$83.30
Purchase #7	$68.27	4.825%	$71.564	$71.56	$71.55	$71.60
7 purchase totals =	$1,023.63		$1,109.8117	$1,109.81	$1,109.80	$1,109.90