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	$135.90	8.369%	$147.2735	$147.27	$147.25	$147.30
Purchase #2	$145.34	11.448%	$161.9785	$161.98	$162.00	$162.00
Purchase #3	$178.83	3.456%	$185.0104	$185.01	$185.00	$185.00
Purchase #4	$79.63	12.263%	$89.395	$89.40	$89.40	$89.40
Purchase #5	$82.44	10.400%	$91.0138	$91.01	$91.00	$91.00
Purchase #6	$136.58	13.460%	$154.9637	$154.96	$154.95	$155.00
Purchase #7	$181.54	8.353%	$196.704	$196.70	$196.70	$196.70
7 purchase totals =	$940.26		$1,026.3389	$1,026.33	$1,026.30	$1,026.40