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	$176.48	3.279%	$182.2668	$182.27	$182.25	$182.30
Purchase #2	$78.82	4.845%	$82.6388	$82.64	$82.65	$82.60
Purchase #3	$250.42	8.723%	$272.2641	$272.26	$272.25	$272.30
Purchase #4	$136.99	3.207%	$141.3833	$141.38	$141.40	$141.40
Purchase #5	$204.73	3.121%	$211.1196	$211.12	$211.10	$211.10
Purchase #6	$53.26	11.371%	$59.3162	$59.32	$59.30	$59.30
Purchase #7	$219.69	5.761%	$232.3463	$232.35	$232.35	$232.30
7 purchase totals =	$1,120.39		$1,181.3351	$1,181.34	$1,181.30	$1,181.30